I'm pretty sure reading through his "incomplete, undocumented" code (that he will not support), and understanding it would take me more time than rewriting it.
Then don't buy it. Not everyone here is a professional developer by day. Many people are lucky to find a few hours on weekends to program. Many people here simply aren't capable of writing this themselves. How many times do you see those people begging for source code to learn from? Even if they end up learning from it and then rewriting it themselves, it's been more than worth $20 to them. People need to learn that some things can be good for some people and not for others without immediately feeling the need to launch an attack because it's no use to them.